I have a complex design for a truss structure i'm designing for work (I work in an architecture firm) and I keep getting various error messages when I try to upload it to the shapeways website. I have used meshlab and netfabb/netfabb cloud to fix the holes and try to fix the flipped triangles. However, when I reuploaded the file, I got this message: "Triangles with mixed winding order were found." I am unsure what exactly this means. I have been trying to work with the shapeways service people, but they just keep sending me to different tutorials, so I figured that I would try posting on here.

Anyone have any suggestions for what to do with my model at this point or ways to fix it? I have included a screenshot of the model just so you can get a feel for what I am talking about.